(a) Explain dominance, codominance and multiple allelism with the help of ABO blood group system.
(b) Explain polygenic inheritance with the help of an example.
Dear student,
Multiple allelism is the phenomenon in which a single trait is controlled by more than two alleles. Although, only two alleles is inherited in the progeny from the parents. Thus, there could be various combinations depending on the number of alleles present. Example - Human blood group shows multiple allelism. There are three alleles present in the human population for blood group, i.e., IA, IB, IO. Every individual possess either homozygous or heterozygous alleles such as IAIA, IAIB, IBIB, IAIO, etc
Co-dominance is the condition in which both the alleles of a particular trait are expressed in a heterozygous condition and both are equally dominant. ABO blood group shows co-dominance because the alleles, IA and IB, are equally dominant when they are expressed in AB blood group. Both these alleles do not interfere with the expression of each other and produce their respective antigens.
On the other hand, the alleles IA and IB are dominant over the allele IO. When allele IO is present with alleles IA or IB, then IO is dominated by the other two alleles. So the blood group will be either A or B . Thus, ABO blood group shows dominance.
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Multiple allelism is the phenomenon in which a single trait is controlled by more than two alleles. Although, only two alleles is inherited in the progeny from the parents. Thus, there could be various combinations depending on the number of alleles present. Example - Human blood group shows multiple allelism. There are three alleles present in the human population for blood group, i.e., IA, IB, IO. Every individual possess either homozygous or heterozygous alleles such as IAIA, IAIB, IBIB, IAIO, etc
Co-dominance is the condition in which both the alleles of a particular trait are expressed in a heterozygous condition and both are equally dominant. ABO blood group shows co-dominance because the alleles, IA and IB, are equally dominant when they are expressed in AB blood group. Both these alleles do not interfere with the expression of each other and produce their respective antigens.
On the other hand, the alleles IA and IB are dominant over the allele IO. When allele IO is present with alleles IA or IB, then IO is dominated by the other two alleles. So the blood group will be either A or B . Thus, ABO blood group shows dominance.
We request you to ask a single quetion in a particular query. You can again post the other question. Our experts are there to help you.
Regards.